1、 Standard Practice Design, Fabrication, and Inspection of Storage Tank Systems for Concentrated Fresh and Process Sulfuric Acid and Oleum at Ambient Temperatures This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provis
2、ions. Its acceptance does not in any respect preclude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to b
3、e construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum
4、requirements and should in no way be interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE Internat
5、ional assumes no responsibility for the interpretation or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of i
6、nterpretations by individual volunteers. Users of this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard
7、 may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard.Users of this NACE International standard are also responsible for establishing appropriate h
8、ealth, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to pe
9、riodic review, and may be revised or withdrawn at any time in accordance with NACE technical committee procedures. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication. The user is cautioned to o
10、btain the latest edition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 281 228-6200).
11、 Approved 2006-12-01 NACE International 1440 South Creek Drive Houston, Texas 77084-4906 +1 281/228-6200 ISBN 1-57590-209-5 2006, NACE International NACE SP0294-2006 (formerly RP0294-94) Item No. 21063 SP0294-2006 NACE International i _ Foreword Sulfuric acid (H2SO4) is the largest-volume corrosive
12、in use today and is generally considered the most important industrial chemical. Large storage tanks containing sulfuric acid or oleum are located in many areas. Carbon steel corrodes moderately when in contact with concentrated sulfuric acid or oleum. If properly designed and adequately maintained,
13、 use of this material is an economical option for storage of these acids at moderate ambient temperatures. However, accelerated corrosion can occur in various forms, and several catastrophic failures that have focused attention on the hazards associated with undetected corrosion have occurred. Large
14、 vertical sulfuric acid storage tanks are usually built to API(1) Standard 650,1and horizontal cylindrical tanks are built to the ASME(2)Boiler and Pressure Vessel Code (BPVC), Section VIII, Division 1.2While these standards/codes provide for sufficient material strength and toughness, they do not a
15、ddress the peculiarities of corrosion by sulfuric acid and oleum. Corrosion allowances and the design for corrosion control in these standards/codes are left to the individual designer, owner, or operator of the tank. This standard provides recommended design, fabrication, and inspection practices f
16、or maintaining the mechanical integrity and minimizing the potential occurrence of undetected corrosion in concentrated fresh sulfuric acid tanks, process sulfuric acid tanks, or oleum storage tanks at atmospheric and low pressure. Inspection guidelines that aid in detecting and monitoring corrosion
17、 are presented, with the overall aim being to avert catastrophic failures. This standard is intended for use by sulfuric acid manufacturers and end users that have stationary sulfuric acid storage tank systems. Rail tank cars, tank trailers, barges, and portable tote containers for sulfuric acid are
18、 not within the scope of this standard. The standard may be used by personnel in many types of roles, including inspectors, plant maintenance personnel, plant engineers, consulting engineers, contract services personnel, etc. A wide variety of industries use sulfuric acid including, but not limited
19、to, the chemical processing, agricultural, pharmaceutical, and hydrocarbon processing industries. This standard was originally prepared by NACE International Task Group T-5A-18, a component of Unit Committee T-5A on Corrosion in Chemical Processes, in 1994. It was technically revised in 2006 by Task
20、 Group (TG) 217. This Task Group was administered by Specific Technology Group (STG) 36 on Process IndustryChemicals, and is also sponsored by STG 03 on Protective Coatings and LiningsImmersion/Buried. This standard is issued by NACE International under the auspices of STG 36. In NACE standards, the
21、 terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements. The term should is used to state something considered good and is recommended but
22、 is not mandatory. The term may is used to state something considered optional. _ _ (1)American Petroleum Institute (API), 1220 L St. NW, Washington, DC 20005-4070. (2)ASME International (ASME), Three Park Ave., New York, NY 10016-5990. SP0294-2006 ii NACE International _ NACE International Standard
23、 Practice Design, Fabrication, and Inspection of Storage Tank Systems for Concentrated Fresh and Process Sulfuric Acid and Oleum at Ambient Temperatures Contents 1. General 1 2. Tank Design Criteria . 2 3. Tank Design Details 5 4. Fabrication and Erection . 9 5. Inspection and Maintenance . 10 6. Sa
24、fety and Environmental Concerns. 16 References 17 Bibliography 19 Appendix A: Physical Properties of Concentrated Sulfuric Acid and Oleum 20 Appendix B: Corrosion-Resistant Alloys 22 Appendix C: Illustrations of Recommended Design 26 Appendix D: Radiographic Acceptance Standard for Welded Equipment
25、in Corrosive Service 36 FIGURES Figure A1: Specific Weight 20 Figure A2: Boiling and Freezing Point 21 Figure B1: Steel Corrosion by Fresh, Stagnant Sulfuric Acid as a Function of Concentration and Temperature . 25 Figure C1: Vertical TankSide Outlet Area 26 Figure C2: Side Manway 27 Figure C3: Hori
26、zontal Tank 28 Figure C4: Vertical Tank 29 Figure C5: Pattern of Side Wall Attack and Ultrasonic Thickness Testing Close to Top Inlet Nozzle 30 Figure C6a: Top Inlet Nozzle . 31 Figure C6b: Alternate Top Inlet Nozzle with Reinforcing Pad (based on API 650, Section 3) . 32 Figure C7: Typical Roof-to-
27、Shell Joints . 33 Figure C8: Bottom Outlet NozzleAlloy Construction. 34 Figure C9: Bottom Outlet Elbow AlternativeAlloy Construction 35 Figure D1: Typical Number and Size of Indications Permitted in Any 150-mm (6.0-in.) Length of Weld Plate Thickness 3.2 mm (0.13 in.) to 13 mm (0.50 in.) 38 Figure D
28、2: Typical Number and Size of Indications Permitted in Any 150-mm (6.0-in.) Length of Weld Plate Thickness 19 mm (0.75 in.) to 31.8 mm (1.25 in.) 39 _SP0294-2006 NACE International 1 _Section 1: General 1.1 This standard provides recommended design, fabrication, and inspection practices for maintain
29、ing the mechanical integrity of and minimizing the potential for the occurrence of undetected corrosion in concentrated fresh sulfuric acid tanks, process sulfuric acid tanks, or oleum storage tanks at atmospheric and low pressure. Inspection guidelines that aid in detecting and monitoring corrosion
30、 are presented, with the overall aim being to avert catastrophic failures. This standard is intended for use by sulfuric acid manufacturers and end users that have stationary sulfuric acid storage tank systems. 1.2 This standard covers the storage of fresh and process sulfuric acids and oleum that m
31、ay be handled in carbon steel equipment. Typical fresh acid concentrations are 93% and 98% sulfuric acid. Process acid is sulfuric acid between 65% and 99.5% concentration that is recycled, purified, and/or concentrated in process units as part of a manufacturing process. Fresh acid and process acid
32、 may be referred to collectively in this standard as concentrated acid. Typical oleum concentrations range up to 65%. 1.3 This standard is intended for bulk acid at ambient temperatures. Situations in which the inlet stream is hotter than 40C (104F), the tank has heaters, or the geographical locatio
33、n results in a metal temperature greater than 40C (104F) require special consideration. In these cases, a materials engineer should be consulted to determine the materials of construction and corrosion allowance (see Paragraphs 2.6 and 2.7 for materials of construction and corrosion allowance consid
34、erations, respectively). 1.4 This standard covers vertical tanks for atmospheric pressure and low pressure built in accordance with API Standard 650 and API Standard 620,3respectively. API 650 covers atmospheric pressure tanks and API 620 covers tanks up to a gauge pressure of 100 kPa (15 psig). Thi
35、s standard covers horizontal tanks built in accordance with ASME Boiler and Pressure Vessel Code (BPVC), Section VIII, Division 1. Vessels pressurized to transfer acid to other vessels without a pump are not in the scope of this standard. 1.5 Spent sulfuric acids from alkylation units and chemical p
36、rocesses can have significantly different corrosion rates from fresh and process sulfuric acid. In addition, there is a potential for deflagration in the vapor space of alkylation and chemical spent sulfuric acid tanks. Therefore, alkylation and chemical spent sulfuric acids are not within the scope
37、 this standard. See NACE Standard RP02054for information on storing alkylation unit spent sulfuric acid. 1.6 Fresh acid typically has very low contaminant levels that do not impact corrosion performance. Sometimes, low levels of hydrogen sulfide (H2S), hydrogen cyanide (HCN), or arsenic (As) may be
38、present in fresh acid, depending on the origin of the raw materials and the manufacturing method. For example, fresh sulfuric acid manufactured with smelter sulfur may contain As. Process sulfuric acid may contain H2S, HCN, or As because of the way it is used in a manufacturing process. Therefore, t
39、he potential effects of H2S, HCN, and As on the corrosion performance of fresh acid and process acid are addressed in this standard. 1.7 This standard is based on good engineering practice. The underlying philosophy is that major failures can be avoided and minor incidents reduced to a minimum by en
40、suring a high degree of storage tank system integrity through good design and construction, followed by adequate and periodic inspection and maintenance. The end user should refer to this standard for guidance, but in all cases, the end user should: Prepare a tank specification that includes design,
41、 materials of construction, fabrication, inspection, and testing. Major acid suppliers can assist by providing examples of their specifications. Select an experienced and qualified designer and tank fabrication and erection contractor. Arrange for inspection during all stages of fabrication and cons
42、truction to ensure the specification is being followed. Operate the tank within design limits. Monitor and maintain the condition of the tank in service through periodic inspection and maintenance. 1.8 This standard applies to all stationary sulfuric acid storage tank systems that contain fresh or p
43、rocess sulfuric acid or oleum at conditions within the scope of this standard. The sulfuric acid storage tank system is defined as the tank and piping internal to the tank and immediately adjacent to the tank, including acid recirculation pump piping loops associated with the tank. Piping up to the
44、first safety device, double block and bleed valves, and appurtenances (e.g., vent goosenecks) are part of the sulfuric acid storage tank system. The sulfuric acid storage tank system also includes the berms, diking, and some tank siting issues. Rail tank cars, tank trailers, barges, and portable tot
45、e containers for sulfuric acid are not within the scope of this standard. 1.9 The symbol % is used throughout this standard to indicate the mass ratio of sulfuric acid to the total mass for sulfuric acid-water mixtures only. 1.10 Appendixes 1.10.1 Appendix A: Physical Properties of Concentrated Sulf
46、uric Acid and Oleum SP0294-2006 2 NACE International 1.10.2 Appendix B: Corrosion-Resistant Alloys 1.10.3 Appendix C: Illustrations of Recommended Design 1.10.4 Appendix D: Radiographic Acceptance Standard for Welded Equipment in Corrosive Service _ Section 2: Tank Design Criteria 2.1 Scope API 620
47、and API 650 contain new tank construction requirements. The design criteria in Sections 2 and 3 of this standard contain additional requirements and recommendations for fresh and process sulfuric acid storage tanks intended to supplement the general tank requirements in API 620 and API 650. Existing
48、 tanks should be checked for compliance with this standard. In the case of notable differences, upgrades should be considered. For existing tanks with designs that differ from this standard, risk-based inspection (RBI) using API 510,5API RP 579,6API RP 580,7API Publication 581,8and API Standard 653,9or equivalent methods, should be used for determining inspection intervals and suitability for continued servic
